Lyocell pulp prepared by mixing bamboo wood and wood cotton and directional treatment process

Abstract

The invention relates to the technical field of chemical fibers, and discloses a process for preparing lyocell pulp by mixing bamboo wood and wood cotton and carrying out directional treatment, which comprises the following steps: bamboo wood pretreatment: sequentially carrying out steam explosion splitting, acid treatment directional silicon removal and biological enzyme assisted delignification on the cut and formed bamboo wood; the raw material wood cotton is sequentially subjected to airflow separation and impurity removal, low-temperature alkali refining and degreasing and biological enzyme deep purification; through a step-by-step directional pretreatment strategy, micro cracks are generated on cell walls of the chopped bamboo fibers through steam explosion, and deep silicon removal of the chopped bamboo fibers is realized without damaging a cellulose skeleton in cooperation with the high-selectivity dissolving capacity of oxalic acid-ammonium fluoride composite acid liquor to silicate; meanwhile, a hemicellulose side chain and a lignin aromatic ring structure are dissociated step by step by a biological enzyme system, and soluble oligomers are removed, so that the spinning blockage risk caused by silicon residues is eliminated on the premise that high-polymerization-degree cellulose of bamboo wood is reserved, and the dissolution smoothness of pulp in an NMMO solvent is guaranteed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chemical fibers, in particular to a process for preparing lyocell pulp by mixing bamboo and wood pulp and directional treatment. BACKGROUND

[0002] Lyocell fiber is made of natural plant fiber and is known as the most valuable product in the history of man-made fiber in nearly half a century. Lyocell has excellent performance of both natural fiber and synthetic fiber. It is a green fiber, and its raw material is cellulose which is inexhaustible in nature. The production process has no chemical reaction, and the solvent used is non-toxic. Lyocell is made of pulp formed by crushing renewable bamboo and wood. The advanced process improves the solvent recovery rate, which is not only energy-saving and environmentally friendly, but also sustainable development. The clothes made of this fiber not only have natural luster and smooth hand feeling, but also have good moisture permeability and air permeability, and the fabric mixed with wool has good effect.

[0003] At present, in the field of lyocell fiber pulp raw material development, due to the regional supply restriction of natural cellulose raw material, the industry generally tries to mix bamboo and wood pulp to expand the source of raw materials. However, in the process of preparing lyocell pulp by mixing bamboo and wood pulp, the compatibility contradiction between high silicon content of bamboo and high lipid content of wood pulp cannot be solved synchronously in the pretreatment process of raw materials.

[0004] Therefore, the present application provides a process for preparing lyocell pulp by mixing bamboo and wood pulp and directional treatment to solve the above problems. SUMMARY

[0005] The main purpose of the present application is to provide a process for preparing lyocell pulp by mixing bamboo and wood pulp and directional treatment to solve the problems raised in the above background.

[0006] To achieve the above purpose, the technical scheme adopted by the present application is as follows: a process for preparing lyocell pulp by mixing bamboo and wood pulp and directional treatment, comprising the following steps: Step 1: bamboo pretreatment: cutting the bamboo into a certain shape and then performing steam explosion defibration, acid treatment directional desiliconization and biological enzyme assisted delignification; Step 2: wood pulp pretreatment: the raw wood pulp is subjected to airflow separation and impurity removal, low-temperature alkali refining and degreasing, and biological enzyme deep purification; Step 3: mixed treatment: mixing the bamboo pulp obtained in step 1 and the wood pulp obtained in step 2 according to the dry weight ratio, adding a dispersing agent for pulp homogenization, wherein the dry weight ratio is 50-70:30-50; Step 4: lyocell pulp forming: washing, dewatering and drying the homogenized pulp to form lyocell pulp; The steam explosion pressure is 1.8-2.2 MPa, and the pressure holding time is 5-8 min. The acid treatment uses a composite acid solution of 1.3-1.8 wt% oxalic acid and 0.08-0.15 wt% ammonium fluoride, with a solid-liquid ratio of 1:10-15. The treatment is carried out in stages: the first stage is held at 45-55℃ for 25-35 min, and the second stage is held at 65-75℃ for 35-45 min. The bio-enzyme-assisted delignification includes the synergistic effect of xylanase, laccase, and mannanase. The low-temperature alkali refining uses a composite emulsion system of 0.4-1.0 wt% alkyl polysaccharide APG and 0.2-0.4 wt% EDTA, with a treatment temperature of less than 75℃ and a time of less than 70 min. The dispersant includes anionic polyacrylate and nonionic hydroxyalkyl cellulose.

[0007] Preferably, in the steam explosion step: The bamboo material is in the form of rectangular bamboo strips, with dimensions of 20±2mm in length, 5±0.5mm in width, and 2±0.2mm in thickness. The moisture content of bamboo is strictly controlled within the range of 40-50%; After blasting, the aspect ratio of the chopped bamboo fibers is 25-30, and the fiber bundles are dispersed in a flocculent manner.

[0008] Preferably, the acid treatment step is followed by a three-stage countercurrent water wash: First stage: Rinse with deionized water until pH is less than 5.0 to remove free silicic acid and residual acid; Second stage: Neutralization treatment with 0.5wt% sodium bicarbonate solution for 10 min; Third stage: Rinse with deionized water until pH is greater than 6.0 and conductivity is less than 50 μS / cm.

[0009] Preferably, the specific conditions for the bio-enzyme-assisted delignification treatment are as follows: First, treat with xylanase: enzyme activity 18-22 IU / g raw material, pH 4.8-5.2, temperature 48-52℃, time 3.5-4.5h, to degrade hemicellulose side chains; Then, the raw material was treated with a laccase-ABTS mediator system: laccase activity 9-11 U / g raw material, ABTS concentration 0.1mM, pH 4.3-4.7, temperature 48-52℃, time 7-9h, to oxidize and degrade lignin. Finally, the raw material was treated with mannanase: enzyme activity 4-6 IU / g, pH 4.8-5.2, temperature 48-52℃, time 1.5-2.5h, to synergistically degrade the hemicellulose backbone.

[0010] Preferably, in the low-temperature alkali refining step: The preferred APG concentration is 0.5-0.8 wt%. When the APG concentration is less than 0.5 wt%, the lipid emulsification rate decreases by 25%. When the APG concentration is greater than 0.8 wt%, the amount of foam increases, which leads to a decrease in the utilization rate of effective ingredients. The amount of EDTA added is 0.28-0.32wt, which chelates calcium ions to prevent pectin cross-linking and repolymerization; The treatment endpoint was determined by a fiber contact angle of less than 30° and a lipid residue of less than 0.5 wt%.

[0011] Preferably, the deep purification by bio-enzymes includes stepwise enzymatic hydrolysis: Step 1: Lipase treatment: Lipase was immobilized on a magnetic Fe3O4@SiO2 carrier with an enzyme activity of 14-16 U / g fiber, pH 7.3-7.7, temperature 43-47℃, time 1.8-2.2h, carrier diameter 100-200nm, and enzyme loading greater than 150mg / g carrier. The second step is pectinase treatment: enzyme activity 28-32 U / g fiber, pH 4.6-5.0, temperature 48-52℃, time 1.8-2.2h.

[0012] Preferably, the kapok fiber after deep purification by the bio-enzyme satisfies the following: The lipid residue is less than 0.2 wt%, the pectin removal rate is greater than 98%, and the degree of fiber polymerization is greater than 1200.

[0013] Preferably, the dispersant system comprises: Sodium polyacrylate: molecular weight 8000-12000, addition amount 0.08-0.12wt%, provides electrostatic repulsion with a zeta potential of -35mV or higher; Hydroxyethyl cellulose: degree of substitution 0.8-1.2, addition amount 0.04-0.06wt%, solution viscosity adjusted to 150-250mPa·s.

[0014] Preferably, in the mixing process step: The dry weight ratio of bamboo pulp to cotton pulp is 58-62:38-42; Homogenization conditions: stirring speed 350-450 rpm, time 40-50 min, temperature 45-55℃; The Lyocell pulp forming step includes: Washing: A counter-current diffusion washer is used, with water consumption of less than 20 m³ / ton of pulp; Dewatering: The double-net press has a line pressure of 80-100 kN / m and a pulp dryness of more than 35%; Drying: The inlet air temperature of the flash dryer is 180-220℃, and the moisture content of the pulp at the outlet is less than 10%.

[0015] Preferably, the lyocell pulp satisfies the following conditions: The α-cellulose content is greater than 93 wt%, the ash content is less than 0.25 wt%, and the lipid residue is less than 0.3 wt%.

[0016] The present invention has the following beneficial effects: 1. In this invention, a stepwise directional pretreatment strategy is adopted. Steam explosion creates microscopic cracks in the cell walls of chopped bamboo fibers. This, combined with the high selectivity of oxalic acid-ammonium fluoride composite acid solution in dissolving silicates, achieves deep desiliconization of chopped bamboo fibers without damaging the cellulose skeleton. At the same time, the bio-enzyme system dissociates hemicellulose side chains and lignin aromatic ring structures stepwise, removing soluble oligomers. This eliminates the risk of spinning blockage caused by silicon residue while retaining the high degree of polymerization of bamboo cellulose, ensuring the smooth dissolution of pulp in NMMO solvent.

[0017] 2. In this invention, the pretreatment stage of kapok involves a two-stage synergistic purification process: during low-temperature alkaline refining, alkyl polysaccharides selectively emulsify lipid molecules, and their hydrophilic ends bind to EDTA, chelating calcium ions and breaking down the pectin-metal ion cross-linking network; in the subsequent deep bio-enzymatic purification, lipase precisely hydrolyzes the ester bonds of triglycerides, while pectinase simultaneously breaks the α-1,4 glycosidic bonds of galacturonic acid, resulting in the gradual degradation of the waxy barrier and pectin matrix on the kapok surface. This forms a clean microporous channel structure on the fiber surface, eliminating lipid-induced solvent decomposition side reactions and improving the accessibility of cellulose reactions.

[0018] 3. In this invention, a bifunctional dispersion system is introduced during the mixing and homogenization stage. Polyacrylate inhibits the flocculation of short bamboo fibers through electrostatic repulsion, while hydroxyalkyl cellulose prevents the entanglement of kapok fibers through steric hindrance. The two work synergistically to form a three-dimensional network in which short bamboo fibers interweave and anchor long kapok fibers. This solves the problem of suspension and stratification caused by differences in fiber morphology, ultimately obtaining a uniformly dispersed and interfacially bonded mixed pulp, providing a foundation for excellent film-forming continuity and mechanical strength of lyocell fibers. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1: A directional processing method for preparing lyocell pulp by mixing bamboo and cotton, comprising the following steps: Step 1: Bamboo pretreatment: The cut bamboo is subjected to steam explosion fiber splitting, acid treatment for directional silicon removal, and bio-enzyme-assisted delignification in sequence; Step 2: Kapok pretreatment: The raw kapok is subjected to airflow separation for impurity removal, low-temperature alkali refining and degreasing, and deep purification by biological enzymes in sequence; Step 3: Mixing treatment: Mix the bamboo pulp obtained in Step 1 with the cotton pulp obtained in Step 2 according to the dry weight ratio, add a dispersant to homogenize the pulp, wherein the dry weight ratio is 50:30; Step 4: Lyocell pulp forming: The homogenized pulp is washed, dehydrated, and dried to produce Lyocell pulp; The steam explosion pressure was 1.8 MPa, and the pressure holding time was 5 min. The acid treatment used a composite acid solution of 1.3 wt% oxalic acid and 0.08 wt% ammonium fluoride with a solid-liquid ratio of 1:10. The treatment was carried out in stages: the first stage was held at 45℃ for 25 min, and the second stage was held at 65℃ for 35 min. The bio-enzyme-assisted delignification included the synergistic effect of xylanase, laccase and mannanase. The low-temperature alkali refining used a composite emulsion system of 0.4 wt% alkyl polysaccharide APG and 0.2 wt% EDTA. The treatment temperature was less than 75℃ and the time was less than 70 min. The dispersants included anionic polyacrylate and nonionic hydroxyalkyl cellulose.

[0021] In the steam explosion process: The bamboo material is in the form of rectangular bamboo strips, with dimensions of 20±2mm in length, 5±0.5mm in width, and 2±0.2mm in thickness. The moisture content of bamboo is strictly controlled at 40%. After blasting, the aspect ratio of the chopped bamboo fibers is 25-30, and the fiber bundles are dispersed in a flocculent manner.

[0022] The acid treatment process is followed by a three-stage countercurrent water wash: First stage: Rinse with deionized water until pH is less than 5.0 to remove free silicic acid and residual acid; Second stage: Neutralization treatment with 0.5wt% sodium bicarbonate solution for 10 min; Third stage: Rinse with deionized water until pH is greater than 6.0 and conductivity is less than 50 μS / cm.

[0023] The specific conditions for enzyme-assisted delignification treatment are as follows: First, treat with xylanase: enzyme activity 18 IU / g raw material, pH 4.8, temperature 48℃, time 3.5h, to degrade hemicellulose side chains; Then, the raw material was treated with a laccase-ABTS mediator system: laccase activity 9 U / g raw material, ABTS concentration 0.1 mM, pH 4.3, temperature 48℃, time 7 h, to oxidize and degrade lignin. Finally, the raw material was treated with mannanase: enzyme activity 4 IU / g raw material, pH 4.8, temperature 48℃, time 1.5h, to synergistically degrade the hemicellulose backbone.

[0024] In the low-temperature alkali refining step: The preferred APG concentration is 0.5 wt%. When the APG concentration is less than 0.5 wt%, the lipid emulsification rate decreases by 25%. When the APG concentration is greater than 0.8 wt%, the amount of foam increases, which leads to a decrease in the utilization rate of the effective ingredients. The amount of EDTA added was 0.28 wt, which chelated calcium ions to prevent pectin cross-linking and repolymerization; The treatment endpoint was determined by a fiber contact angle of less than 30° and a lipid residue of less than 0.5 wt%.

[0025] Deep purification using bio-enzymes includes stepwise enzymatic hydrolysis: Step 1: Lipase treatment: Lipase was immobilized on a magnetic Fe3O4SiO2 carrier with an enzyme activity of 14 U / g fiber, pH 7.3, temperature 43℃, time 1.8h, carrier diameter 100nm, and enzyme loading greater than 150mg / g carrier. The second step is pectinase treatment: enzyme activity 28 U / g fiber, pH 4.6, temperature 48℃, time 1.8h.

[0026] The kapok fiber, after deep purification by bio-enzymes, meets the following requirements: The lipid residue is less than 0.2 wt%, the pectin removal rate is greater than 98%, and the degree of fiber polymerization is greater than 1200.

[0027] The dispersant system includes: Sodium polyacrylate: molecular weight 8000, addition amount 0.08wt%, provides electrostatic repulsion with a zeta potential of -35mV or higher; Hydroxyethyl cellulose: degree of substitution 0.8, addition amount 0.04 wt%, solution viscosity adjusted to 150 mPa·s.

[0028] In the mixing process: The dry weight ratio of bamboo pulp to cotton pulp is 58:38; Homogenization conditions: stirring speed 350 rpm, time 40 min, temperature 45℃; Lyocell pulp forming steps include: Washing: A counter-current diffusion washer is used, with water consumption of less than 20 m³ / ton of pulp; Dewatering: The double-net press has a line pressure of 80kN / m and a pulp dryness of more than 35%; Drying: The inlet air temperature of the flash dryer is 180℃, and the moisture content of the pulp at the outlet is less than 10%.

[0029] Lyocell pulp satisfies: The α-cellulose content is greater than 93 wt%, the ash content is less than 0.25 wt%, and the lipid residue is less than 0.3 wt%.

[0030] Example 2: Targeted processing technology for preparing lyocell pulp by mixing bamboo and cotton, including the following steps: Includes the following steps: Step 1: Bamboo pretreatment: The cut bamboo is subjected to steam explosion fiber splitting, acid treatment for directional silicon removal, and bio-enzyme-assisted delignification in sequence; Step 2: Kapok pretreatment: The raw kapok is subjected to airflow separation for impurity removal, low-temperature alkali refining and degreasing, and deep purification by biological enzymes in sequence; Step 3: Mixing treatment: Mix the bamboo pulp obtained in Step 1 with the cotton pulp obtained in Step 2 according to the dry weight ratio, add a dispersant to homogenize the pulp, wherein the dry weight ratio is 60:40; Step 4: Lyocell pulp forming: The homogenized pulp is washed, dehydrated, and dried to produce Lyocell pulp; The steam explosion pressure was 2.0 MPa, and the pressure holding time was 6 min. The acid treatment used a composite acid solution of 1.5 wt% oxalic acid and 0.10 wt% ammonium fluoride with a solid-liquid ratio of 1:12. The treatment was carried out in stages: the first stage was held at 50℃ for 30 min, and the second stage was held at 70℃ for 40 min. The bio-enzyme-assisted delignification included the synergistic effect of xylanase, laccase and mannanase. The low-temperature alkali refining used a composite emulsion system of 0.6 wt% alkyl polysaccharide APG and 0.3 wt% EDTA. The treatment temperature was less than 75℃ and the time was less than 70 min. The dispersants included anionic polyacrylate and nonionic hydroxyalkyl cellulose.

[0031] In the steam explosion process: The bamboo material is in the form of rectangular bamboo strips, with dimensions of 20±2mm in length, 5±0.5mm in width, and 2±0.2mm in thickness. The moisture content of bamboo is strictly controlled within 45%; After blasting, the aspect ratio of the chopped bamboo fibers is 28, and the fiber bundles are dispersed in a flocculent manner.

[0032] The acid treatment process is followed by a three-stage countercurrent water wash: First stage: Rinse with deionized water until pH is less than 5.0 to remove free silicic acid and residual acid; Second stage: Neutralization treatment with 0.5wt% sodium bicarbonate solution for 10 min; Third stage: Rinse with deionized water until pH is greater than 6.0 and conductivity is less than 50 μS / cm.

[0033] The specific conditions for enzyme-assisted delignification treatment are as follows: First, treat with xylanase: enzyme activity 20 IU / g raw material, pH 5.0, temperature 50℃, time 4.0h, to degrade hemicellulose side chains; Then, the raw material was treated with a laccase-ABTS mediator system: laccase activity 10 U / g raw material, ABTS concentration 0.1 mM, pH 4.5, temperature 50℃, time 8h, to oxidize and degrade lignin. Finally, the raw material was treated with mannanase: enzyme activity 5 U / g, pH 5.0, temperature 50℃, time 2.0h, to synergistically degrade the hemicellulose backbone.

[0034] In the low-temperature alkali refining step: The preferred APG concentration is 0.6 wt%. When the APG concentration is less than 0.5 wt%, the lipid emulsification rate decreases by 25%. When the APG concentration is greater than 0.8 wt%, the amount of foam increases, which leads to a decrease in the utilization rate of the effective ingredients. The amount of EDTA added is 0.30wt, which chelates calcium ions to prevent pectin cross-linking and repolymerization; The treatment endpoint was determined by a fiber contact angle of less than 30° and a lipid residue of less than 0.5 wt%.

[0035] Deep purification using bio-enzymes includes stepwise enzymatic hydrolysis: Step 1: Lipase treatment: Lipase was immobilized on a magnetic Fe3O4SiO2 carrier with an enzyme activity of 15 U / g fiber, pH 7.5, temperature 45℃, time 2.0 h, carrier diameter 150 nm, and enzyme loading greater than 150 mg / g carrier. The second step is pectinase treatment: enzyme activity 30 U / g fiber, pH 4.8, temperature 50℃, time 2.0h.

[0036] The kapok fiber, after deep purification by bio-enzymes, meets the following requirements: The lipid residue is less than 0.2 wt%, the pectin removal rate is greater than 98%, and the degree of fiber polymerization is greater than 1200.

[0037] The dispersant system includes: Sodium polyacrylate: molecular weight 10000, addition amount 0.10wt%, provides electrostatic repulsion with a zeta potential of -35mV or higher; Hydroxyethyl cellulose: degree of substitution 1.0, addition amount 0.05wt%, solution viscosity adjusted to 200mPa·s.

[0038] In the mixing process: The dry weight ratio of bamboo pulp to cotton pulp is 60:40; Homogenization conditions: stirring speed 400 rpm, time 45 min, temperature 50℃; Lyocell pulp forming steps include: Washing: A counter-current diffusion washer is used, with water consumption of less than 20 m³ / ton of pulp; Dewatering: The double-net press has a line pressure of 90kN / m and a pulp dryness of more than 35%; Drying: The inlet air temperature of the flash dryer is 200℃, and the moisture content of the pulp at the outlet is less than 10%.

[0039] Lyocell pulp satisfies: The α-cellulose content is greater than 93 wt%, the ash content is less than 0.25 wt%, and the lipid residue is less than 0.3 wt%.

[0040] Example 3: Targeted processing technology for preparing lyocell pulp by mixing bamboo and cotton, including the following steps: Step 1: Bamboo pretreatment: The cut bamboo is subjected to steam explosion fiber splitting, acid treatment for directional silicon removal, and bio-enzyme-assisted delignification in sequence; Step 2: Kapok pretreatment: The raw kapok is subjected to airflow separation for impurity removal, low-temperature alkali refining and degreasing, and deep purification by biological enzymes in sequence; Step 3: Mixing treatment: Mix the bamboo pulp obtained in Step 1 and the cotton pulp obtained in Step 2 according to the dry weight ratio, and add a dispersant to homogenize the pulp, wherein the dry weight ratio is 70:50; Step 4: Lyocell pulp forming: The homogenized pulp is washed, dehydrated, and dried to produce Lyocell pulp; The steam explosion pressure was 2.2 MPa, and the pressure holding time was 8 min. The acid treatment used a composite acid solution of 1.8 wt% oxalic acid and 0.15 wt% ammonium fluoride with a solid-liquid ratio of 1:15. The treatment was carried out in stages: the first stage was held at 55℃ for 35 min, and the second stage was held at 75℃ for 45 min. The bio-enzyme-assisted delignification included the synergistic effect of xylanase, laccase, and mannanase. The low-temperature alkali refining used a composite emulsion system of 1.0 wt% alkyl polysaccharide APG and 0.4 wt% EDTA. The treatment temperature was less than 75℃ and the time was less than 70 min. The dispersants included anionic polyacrylate and nonionic hydroxyalkyl cellulose.

[0041] In the steam explosion process: The bamboo material is in the form of rectangular bamboo strips, with dimensions of 20±2mm in length, 5±0.5mm in width, and 2±0.2mm in thickness. The moisture content of bamboo is strictly controlled to be below 50%; After blasting, the aspect ratio of the chopped bamboo fibers is 30, and the fiber bundles are dispersed in a flocculent manner.

[0042] The acid treatment process is followed by a three-stage countercurrent water wash: First stage: Rinse with deionized water until pH is less than 5.0 to remove free silicic acid and residual acid; Second stage: Neutralization treatment with 0.5wt% sodium bicarbonate solution for 10 min; Third stage: Rinse with deionized water until pH is greater than 6.0 and conductivity is less than 50 μS / cm.

[0043] The specific conditions for enzyme-assisted delignification treatment are as follows: First, treat with xylanase: enzyme activity 22 IU / g raw material, pH 5.2, temperature 52℃, time 4.5h, to degrade hemicellulose side chains; Then, the raw material was treated with a laccase-ABTS mediator system: laccase activity 11 U / g raw material, ABTS concentration 0.1 mM, pH 4.7, temperature 52℃, time 9 h, to oxidize and degrade lignin. Finally, the raw material was treated with mannanase: enzyme activity 6 U / g, pH 5.2, temperature 52℃, time 2.5h, to synergistically degrade the hemicellulose backbone.

[0044] In the low-temperature alkali refining step: The preferred APG concentration is 0.8 wt%. When the APG concentration is less than 0.5 wt%, the lipid emulsification rate decreases by 25%. When the APG concentration is greater than 0.8 wt%, the amount of foam increases, which leads to a decrease in the utilization rate of effective ingredients. The amount of EDTA added was 0.32wt, which chelated calcium ions to prevent pectin cross-linking and repolymerization; The treatment endpoint was determined by a fiber contact angle of less than 30° and a lipid residue of less than 0.5 wt%.

[0045] Deep purification using bio-enzymes includes stepwise enzymatic hydrolysis: Step 1: Lipase treatment: Lipase was immobilized on a magnetic Fe3O4SiO2 carrier with an enzyme activity of 14-16 U / g fiber, pH 7.7, temperature 47℃, time 2.2h, carrier diameter 200nm, and enzyme loading greater than 150mg / g carrier. The second step is pectinase treatment: enzyme activity 32 U / g fiber, pH 5.0, temperature 52℃, time 2.2h.

[0046] The kapok fiber, after deep purification by bio-enzymes, meets the following requirements: The lipid residue is less than 0.2 wt%, the pectin removal rate is greater than 98%, and the degree of fiber polymerization is greater than 1200.

[0047] The dispersant system includes: Sodium polyacrylate: molecular weight 12000, addition amount 0.12wt%, provides electrostatic repulsion with a zeta potential of -35mV or higher; Hydroxyethyl cellulose: degree of substitution 1.2, addition amount 0.06wt%, solution viscosity adjusted to 250mPa·s.

[0048] In the mixing process: The dry weight ratio of bamboo pulp to cotton pulp is 62:42; Homogenization conditions: stirring speed 450 rpm, time 50 min, temperature 55℃; Lyocell pulp forming steps include: Washing: A counter-current diffusion washer is used, with water consumption of less than 20 m³ / ton of pulp; Dewatering: The double-net press has a line pressure of 100kN / m and a pulp dryness of more than 35%; Drying: The inlet air temperature of the flash dryer is 220℃, and the moisture content of the pulp at the outlet is less than 10%.

[0049] Lyocell pulp satisfies: The α-cellulose content is greater than 93 wt%, the ash content is less than 0.25 wt%, and the lipid residue is less than 0.3 wt%.

[0050] Comparative Example 1: The difference between this comparative example and Examples 1-3 is that no ammonium fluoride desiliconizing agent was added during the bamboo pretreatment.

[0051] Comparative Example 2: The difference between this comparative example and Examples 1-3 is that no lipase was used for deep degreasing during the pretreatment of kapok.

[0052] Comparative Example 3: The difference between this comparative example and Examples 1-3 is that fiber grading and homogenization were not performed during the mixing process.

[0053] Comparative Example 4: The difference between this comparative example and Examples 1-3 is that no hydroxyalkyl cellulose dispersant was added to the mixed slurry.

[0054] The performance of the bamboo and cotton mixed lyocell pulp prepared in Examples 1-3 and Comparative Examples 1-4 was tested: α-cellulose content test: Weigh 2.00g of oven-dried pulp, treat it with 17.5% NaOH solution at 20℃ for 30min, filter, wash, dry and weigh, and calculate the cellulose purity; Gel particle count test: The pulp was prepared into a 12% NMMO solution with 13% water content, dissolved at 85℃ for 120 min, and the number of insoluble matter larger than 10μm was detected by laser particle size analyzer. Lipid residue test: The extract was circulated for 6 hours using a Soxhlet extractor with ether as the solvent, and the percentage of the extract relative to the oven-dried pulp mass was calculated. Degree of polymerization (DP) test: The intrinsic viscosity of the fiber is determined by the copper ethylenediamine method and the average degree of polymerization is calculated.

[0055] The test data of the bamboo and cotton mixed Lyocell pulp prepared in Examples 1-3 and Comparative Examples 1-4 are recorded in the table below: Group Alpha-cellulose Silicon residue Lipid residue Dispersion index Gel number Filter flux Example 1 93.5 0.08 0.18 0.21 3 215 Example 2 94.1 0.05 0.16 0.18 2 230 Example 3 93.8 0.07 0.17 0.19 4 225 Comparative Example 1 89.2 0.41 0.19 0.23 185 95 Comparative Example 2 90.7 0.06 0.83 0.27 102 110 Comparative Example 3 92.3 0.09 0.21 0.39 67 135 Comparative Example 4 91.6 0.07 0.20 0.26 48 155 Comparison and analysis of the data in the table show that the bamboo and kapok mixed lyocell pulp prepared using the processes of Examples 1-3 exhibits improved performance compared to the pulp prepared using the processes of Comparative Examples 1-4. This indicates that the stepwise directional pretreatment strategy, through steam explosion creating microscopic cracks in the cell walls of chopped bamboo fibers, combined with the highly selective dissolution capacity of the oxalic acid-ammonium fluoride composite acid solution on silicates, achieves deep desiliconization of chopped bamboo fibers without damaging the cellulose skeleton. Simultaneously, the bio-enzyme system stepwise dissociates hemicellulose side chains and lignin aromatic ring structures, removing soluble oligomers, thereby preserving the properties of the bamboo. Under the premise of high-polymerization cellulose, the risk of spinning blockage caused by silicon residue is eliminated, ensuring the smooth dissolution of pulp in NMMO solvent. In the kapok pretreatment stage, a two-stage synergistic purification is carried out: in the low-temperature alkali refining, alkyl polysaccharides selectively emulsify lipid molecules, and their hydrophilic ends combine with EDTA to chelate calcium ions, breaking down the pectin-metal ion cross-linking network; in the subsequent deep purification by bioenzymes, lipases precisely hydrolyze the ester bonds of triglycerides, and pectinase simultaneously breaks the α-1,4 glycosidic bonds of galacturonic acid, so that the waxy barrier and pectin matrix on the surface of kapok are degraded layer by layer. This forms a clean microporous channel structure on the fiber surface, eliminates lipid-induced solvent decomposition side reactions, and improves the accessibility of cellulose reaction; in the mixing and homogenization stage, a bifunctional dispersion system is introduced. Polyacrylate inhibits the flocculation of short bamboo fibers through electrostatic repulsion, while hydroxyalkyl cellulose prevents kapok fiber entanglement through steric hindrance. The two work together to form a three-dimensional network of "short bamboo fibers interspersed and anchored to long kapok fibers". The problem of suspension and stratification caused by differences in fiber morphology is solved, and a uniformly dispersed and interfacially bonded mixed pulp is finally obtained, which provides an excellent basis for the film-forming continuity and mechanical strength of Lyocell fibers.

[0056] As a green and environmentally friendly fiber of the 21st century, Lyocell uses renewable plant-derived pulp as raw material, and its processing technology is environmentally friendly and its waste is biodegradable. It is considered a sustainable fiber with a complete life cycle.

[0057] The production process of bamboo pulp lyocell fiber follows a route of dry crushing, direct dissolution, and dry-jet wet spinning. The process uses bamboo pulp as the starting material and involves 18-20 rigorous steps, including bamboo pulp processing, pulp crushing, and solvent application. Notably, the entire production process involves almost no chemical reactions, primarily physical reactions, thus ensuring the product's environmental performance. The bamboo pulp used in the production process is a fast-growing plant and a renewable and recyclable material, and the solvent N-methylmorpholine-N-oxide is non-toxic and pollution-free. After special processing and equipment, 99.7% of the solvent can be recovered and recycled. This production process truly achieves zero emissions, and the product is biodegradable and environmentally friendly.

[0058] By comparing and analyzing the relevant data in the table, it can be seen that the bamboo and kapok mixed lyocell pulp prepared by the process of the present invention not only has high purity, low impurity residue and excellent solubility, but also shows that the bamboo and kapok mixed lyocell pulp preparation process provided by the present invention, through the triple innovation of raw material staged directional treatment, fiber interface regulation and dissolution structure optimization, improves resource utilization and product added value, has a broader market prospect and is more suitable for promotion.

[0059] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A process for the directional treatment of lyocell pulp prepared by mixing bamboo and cotton, characterized in that, Includes the following steps: Step 1: Bamboo pretreatment: The cut bamboo is subjected to steam explosion fiber splitting, acid treatment for directional silicon removal, and bio-enzyme-assisted delignification in sequence; Step 2: Kapok pretreatment: The raw kapok is subjected to airflow sorting for impurity removal, low-temperature alkali refining and degreasing, and deep purification by biological enzymes in sequence; Step 3: Mixing treatment: Mix the bamboo pulp obtained in Step 1 with the cotton pulp obtained in Step 2 according to the dry weight ratio, add a dispersant to homogenize the pulp, wherein the dry weight ratio is 50-70:30-50; Step 4: Lyocell pulp forming: The homogenized pulp is washed, dehydrated, and dried to produce Lyocell pulp; The steam explosion pressure is 1.8-2.2 MPa, and the pressure holding time is 5-8 min. The acid treatment uses a composite acid solution of 1.3-1.8 wt% oxalic acid and 0.08-0.15 wt% ammonium fluoride, with a solid-liquid ratio of 1:10-15. The treatment is carried out in stages: the first stage is held at 45-55℃ for 25-35 min, and the second stage is held at 65-75℃ for 35-45 min. The bio-enzyme-assisted delignification includes the synergistic effect of xylanase, laccase, and mannanase. The low-temperature alkali refining uses a composite emulsion system of 0.4-1.0 wt% alkyl polysaccharide APG and 0.2-0.4 wt% EDTA, with a treatment temperature of less than 75℃ and a time of less than 70 min. The dispersant includes anionic polyacrylate and nonionic hydroxyalkyl cellulose.

2. The directional processing technology for preparing lyocell pulp by mixing bamboo and cotton according to claim 1, characterized in that, In the steam explosion step: The bamboo material is in the form of rectangular bamboo strips, with dimensions of 20±2mm in length, 5±0.5mm in width, and 2±0.2mm in thickness. The moisture content of bamboo is strictly controlled within the range of 40-50%; After blasting, the aspect ratio of the chopped bamboo fibers is 25-30, and the fiber bundles are dispersed in a flocculent manner.

3. The directional processing technology for preparing lyocell pulp by mixing bamboo and cotton according to claim 1, characterized in that, The acid treatment step is followed by a three-stage countercurrent water wash: First stage: Rinse with deionized water until pH is less than 5.0 to remove free silicic acid and residual acid; Second stage: Neutralization treatment with 0.5wt% sodium bicarbonate solution for 10 min; Third stage: Rinse with deionized water until pH is greater than 6.0 and conductivity is less than 50 μS / cm.

4. The directional processing technology for preparing lyocell pulp by mixing bamboo and cotton according to claim 1, characterized in that, The specific conditions for the bio-enzyme-assisted delignification treatment are as follows: First, treat with xylanase: enzyme activity 18-22 IU / g raw material, pH 4.8-5.2, temperature 48-52℃, time 3.5-4.5h, to degrade hemicellulose side chains; Then, the raw material was treated with a laccase-ABTS mediator system: laccase activity 9-11 U / g raw material, ABTS concentration 0.1mM, pH 4.3-4.7, temperature 48-52℃, time 7-9h, to oxidize and degrade lignin. Finally, mannanase was used for treatment: enzyme activity 4-6 U / g raw material, pH 4.8-5.2, temperature 48-52℃, time 1.5-2.5h, to synergistically degrade the hemicellulose backbone.

5. The directional processing technology for preparing lyocell pulp by mixing bamboo and cotton according to claim 1, characterized in that, In the aforementioned low-temperature alkali refining step: The APG concentration is 0.5-0.8 wt%. When the APG concentration is less than 0.5 wt%, the lipid emulsification rate decreases by 25%. When the APG concentration is greater than 0.8 wt%, the amount of foam increases, which leads to a decrease in the utilization rate of effective ingredients. The amount of EDTA added is 0.28-0.32wt, which chelates calcium ions to prevent pectin cross-linking and repolymerization; The treatment endpoint was determined by a fiber contact angle of less than 30° and a lipid residue of less than 0.5 wt%.

6. The directional processing technology for preparing lyocell pulp by mixing bamboo and cotton according to claim 1, characterized in that, The deep purification process using bio-enzymes includes stepwise enzymatic hydrolysis: Step 1: Lipase treatment: Lipase was immobilized on a magnetic Fe3O4SiO2 carrier with an enzyme activity of 14-16 U / g fiber, pH 7.3-7.7, temperature 43-47℃, time 1.8-2.2h, carrier diameter 100-200nm, and enzyme loading greater than 150mg / g carrier. The second step is pectinase treatment: enzyme activity 28-32 U / g fiber, pH 4.6-5.0, temperature 48-52℃, time 1.8-2.2h.

7. The directional processing technology for preparing lyocell pulp by mixing bamboo and cotton according to claim 1, characterized in that, The kapok fiber, after deep purification by bio-enzymes, meets the following requirements: The lipid residue is less than 0.2 wt%, the pectin removal rate is greater than 98%, and the degree of fiber polymerization is greater than 1200.

8. The directional processing technology for preparing lyocell pulp by mixing bamboo and cotton according to claim 1, characterized in that, The dispersant system comprises: Sodium polyacrylate: molecular weight 8000-12000, addition amount 0.08-0.12wt%, provides electrostatic repulsion with a zeta potential of -35mV or higher; Hydroxyethyl cellulose: degree of substitution 0.8-1.2, addition amount 0.04-0.06wt%, solution viscosity adjusted to 150-250mPa·s.

9. The directional processing technology for preparing lyocell pulp by mixing bamboo and cotton according to claim 1, characterized in that, In the mixing process step: The dry weight ratio of bamboo pulp to cotton pulp is 58-62:38-42; Homogenization conditions: stirring speed 350-450 rpm, time 40-50 min, temperature 45-55℃; The Lyocell pulp forming step includes: Washing: A counter-current diffusion washer is used, with water consumption of less than 20 m³ / ton of pulp; Dewatering: The double-net press has a line pressure of 80-100 kN / m and a pulp dryness of more than 35%; Drying: The inlet air temperature of the flash dryer is 180-220℃, and the moisture content of the pulp at the outlet is less than 10%.

10. A mixture of bamboo and cotton wool lyocell pulp prepared by any one of the processes described in claims 1-9, characterized in that, The Lyocell pulp satisfies the following: The α-cellulose content is greater than 93 wt%, the ash content is less than 0.25 wt%, and the lipid residue is less than 0.3 wt%.